Composite sheets comprising two sheets joined by material closure are commonly known from the prior art. For example composite sheets designated as double layer sheets are frequently used in the construction of vehicles due to their high rigidity at relatively low weight. For example, a double layer sheet, which consists of two cover sheets, wherein at least one of the coversheets is designed as a studded plate and the studded plate is joined to the other cover sheet with its knob points by material closure, is known from European Patent EP 1 062 397 B1. The studded plate, however, is almost limited in application to flat components. In addition, sandwich sheets with a plastic core are known; their scope of application likewise being limited only to certain areas, for example the bonnet (i.e. hood), the roof or the outer door sheet of a vehicle. Both variants lack load capacity in case of great deformations, as can result in case of a crash for example. Therefore it is desirable to improve the forming behavior and the load capacity in case of high forming degrees of the prior art composite sheets, so that the scope of application of the composite sheets comprising two sheets joined by material closure can be extended.